spaceport logistics

electricity can be used 

to combine carbon from air 

and hydrogen from water 

into methane gas 

which can be used as rocket fuel 

so if spaceports are placed by the sea 

then industrial facilities at the spaceport 

can be used to turn air and seawater into rocket fuel 

and if there is too little carbon in the air 

then coal, wood or trash could be used as a source of carbon 

so that electricity is used 

to combine carbon from coal, wood or trash

and hydrogen from water 

into methane gas 

which can be used as rocket fuel